The AHAS gene of Cichorium intybus is expressed in fast growing and inflorescential organs

Expression of acetohydroxy acid synthase (AHAS, EC 4.1.3.18) was analysed i n biennial chicory (Cichorium intybus L. cv. Witloof) by northern blot anal ysis and enzyme assays. Young plantlets displayed high enzyme activity and AHAS mRNA accumulation in the root and the young leaves. Conversely, both e nzyme activity and AHAS mRNA were undetectable in the mature tuberous tapro ot produced at the end of the first year. When such a taproot is grown in d arkness, it develops an etiolated bud (the chicon) in which enzyme activity and AHAS mRNA are located in the neoformed lateral roots and the youngest central leaves. When this root is grown in the light, it produces a floral stem with many capitules, AHAS activities as well as AHAS mRNA were at the highest in capitules bearing developing seeds. However, AHAS seems strongly expressed in the young and developing tissues which need amino acids for p rotein synthesis and tightly associated to carbon influx whenever it is pro vided by photosynthesis or fructan remobilization.